I thought it would be neat to put a large piece of paper and a marker on the door. You ask the question "Who are you and where are you from?" at the top. Much like a high school year book signing. Everybody say's a little something. I bet there are people all over (even the crew). I would be afraid that unattended kids would get the marker and do something stupid.
Cabin numbers work great unless you make that wrong turn coming off the elevator! I don't know how many times I did that!